Changing Concentrations of Methyl Halides, Nonmethane Hydrocarbons, Organic Sulfur Species, and Alkyl Nitrates in Response to Iron Fertilization during SOFeX

New Mexico Institute Of Mining And Technology, Socorro NM

Investigators

Abstract

ABSTRACT OCE-0327198 Marine production and consumption of volatile organic carbon (VOC) species, including methyl halides, nonmethane hydrocarbons (NMHCs), alkyl nitrates, and dimethyl sulfide (DMS), by phytoplankton and other microorganisms have an impact on stratospheric ozone and global climate. Several VOCs were sampled from surface ocean water and the lower atmosphere for the first time during an iron (Fe) enrichment experiment. The Southern Ocean Iron Experiment (SOFeX) was conducted between January-February 2002, and involved the research vessels Revelle, Melville, and Polar Star. An extensive suite of chemical, physical, and biological measurements were made in order to observe the effects of iron fertilization on marine organisms and the extent of carbon sequestration in two high nutrient, low chlorophyll (HNLC) regions in the Southern Ocean. Previous iron enrichment experiments indicate that primary productivity is limited by trace amounts of iron in certain HNLC regions. During SOFeX, two areas were fertilized, one north of the Antarctic Polar Front and the other south of the front. Roughly one quarter of the ocean.s surface waters are HNLC and may be iron limited. Much of this area is in the Southern Ocean, making this region promising for reducing global warming by sequestering additional oceanic carbon by iron fertilization. To date, researchers at the New Mexico Institute of Mining and Technology have completed VOC analyses of 420 seawater samples from SOFeX. With support from this project, they will complete the remaining 98% of the analysis, so that each peak representing each compound on 2700 individual chromatograms can be visually checked, normalized to the standards, and corrected for disequilibria in the equilibrator. The U.S. and other governments are seeking solutions to mitigate global warming. Some proposals involve climate engineering such as iron fertilization. Prudence dictates that before any large-scale oceanic iron fertilization takes place, its impact on the marine production of climatically relevant compounds such as VOCs must be assessed. VOC results from the SOFeX field study will better inform policy makers and society on the coupling between the marine biosphere and the atmosphere. This knowledge is imperative in order to more fully understand the climatic ramifications of proposed large-scale iron fertilization/carbon sequestration.